V.1-3 Some said they did not believe that he was really an apostle.
V.3 They asked Paul for a proof.
V.5 His answer. “Examine yourselves — are you saved — through whose preaching were you saved?” Of course they would have to admit that it was through the preaching of Paul, so he says, “This is your proof that Christ has been speaking through me.”
V.11 Paul had not found it easy to write these 2 letters. He loved those believers so much, and it hurt him to have to warn and correct them. Now that it is ended, he speaks so gently, “Finally brethren farewell.” If we belong to our Lord Jesus we are truly “brethren” and can happily greet one another this way. “Be perfect” — he wished nothing less for them than true and faithful following of the Lord. “Be of good comfort” — He knew what it was to be comforted in trial, and he wished them to know it too. “Be of one mind, live in peace.” Do we desire this?